1. Field of the Invention
The present application is based on Japanese Patent Applications No. 2009-147993 and 2010-048790, filed on Jun. 22, 2009 and Mar. 5, 2010, the entire contents of which are hereby incorporated by reference.
The present invention relates to a piezoelectric thin film element using lithium potassium sodium niobate and a manufacturing method of the same, and a piezoelectric thin film device.
2. Description of the Related Art
A piezoelectric body is processed into various piezoelectric elements according to various purposes, and is widely used as an actuator for generating deformation by applied voltage, and a functional electronic component such as a sensor for generating the voltage from the deformation of the piezoelectric element. A lead-based dielectric material having large piezoelectric characteristics is generally known as the piezoelectric body utilized for the purpose of usage in the actuator and the sensor. Particularly, Pb(Zr1−xTix)O3-based perovskite ferroelectric material called PZT has been generally known heretofore. Ordinarily, these piezoelectric materials are formed by sintering an oxide made of a piezoelectric material.
Meanwhile, in recent years, development of the piezoelectric substance not containing lead is desired from the consideration of an environment, and development of sodium potassium lithium niobate (general formula: (NaxKyLiz)NbO3 (0<x<1, 0<y<1, 0<z<1, x+y+z=1), etc, has been progressed. The sodium potassium lithium niobate has the piezoelectric characteristics comparable to PZT, and therefore is expected as a dominant candidate of the non-lead piezoelectric material.
At present, as downsizing and higher performance of each kind of electronic component is progressed, the downsizing and higher performance are also required in the piezoelectric element. However, in a piezoelectric material manufactured by a manufacturing method typified by a sintering method, being a method performed conventionally, as its thickness becomes thinner, particularly as the thickness becomes closer to the thickness of about 10 μm, this thickness becomes closer to the size of a crystal grain constituting the material, and its influence can not be ignored. This involves a problem that variation and deterioration of the characteristics is remarkable, and in order to avoid this problem, a forming method of the piezoelectric substance applying a thin film technique in place of the sintering method has been studied in recent years.
In recent years, a PZT piezoelectric thin film formed by RF sputtering method is put to practical use as an actuator for a head of highly precise high speed ink jet printer or a small-sized and inexpensive gyro sensor (for example, see patent document 1 and non-patent document 1). Further, the piezoelectric thin film element using a piezoelectric thin film made of lithium potassium sodium niobate not using lead is also proposed (for example, see patent document 3).
(Patent Documents)
    (Patent document 1) Japanese Patent Laid Open Publication No. 10-286953    (Patent document 2) Japanese Patent Laid Open Publication No. 2007-19302    (Patent document 3) Japanese Patent Laid Open Publication No. 2007-184513(Non-Patent Document)    (Non-patent document 1) High performance and advanced application technology of piezoelectric material (published by science & technology in 2007) supervised by Kiyoshi Nakamura
The head for highly precise high speed ink jet printer or the small-sized and inexpensive gyro sensor with low environmental load can be fabricated, by forming a non-lead piezoelectric thin film as the piezoelectric thin film. As a specific candidate thereof, basic study on a thinner film of the lithium potassium sodium niobate has been progressed. However, in a conventional art, the non-lead piezoelectric thin film element and piezoelectric thin film device satisfying a requested performance can not be stably provided.